Hydraulic turbine



Aug. 21, 1928.

L. F. MOODY HYDRAULIC TURBINE Filed Nov. 15, 1923 3 Sheets-Sheet W INVENTOR Z E n W :d-Z ZZTORNEZ Aug. 21, 1928. 1,681,706

L. F. MOODY HYDRAULI C TURBI NE Filed NovflS, 192s 5 Sheets-Sheet 2 INVENTOR Aug. 21, 1928. 1,681,706

L. F. MOODY HYDRAULI C TURBI NE Filed Nov. 13, 1923 3 Sheets-Sheet 3 Patented Aug. 21, 1928.

' LEWIS'FERRY MOODY, orrmnapnnrnra, PENNSYLVANIA. 1

HYDRAULIC TURBINE.

This invention relates to hydraulic turbines and particularly to draft tubes for the same. The objectof. the invention is to provide a draft tube which While simple and inexpensive in construction will be ell'lcient in operation and especially adapted to decelerate the flow within a limited space. An other object of the invention is to provide a 'drafttube suitable for turbines of high spe- Further objects of the invention, particularly inprovidinga drafttube structure havin g a series of concentric annular passages'in positionbelow the runner, will appear; from the following description and the accompanying drawings. r

' B-y dividing the drafttube passage into a number of passages each receiving apart of the total flow, itbecomes posslble to'decelerate the velocity of discharge from the runncliimd to convert its kinetic energy into useful head within a smaller space than would be possible if. a single passage were used, and to accomplish this without sacrifice of draft tube ellicien-cy. The reason why this can be accomplished may be understood by considering asirnple passage of rectangw l ar cross-section having a pair'of opposite sides diverging at. a small angle. Such a passage will decelerate the. flow, and it is known. that the eflifciency of the energy conversion is dependent on theangle of divergence of the sides; It the angle'is increased beyond the best value in the elforttoproduce the deceleration in a shorter length} of passage, internal edidiesare caused in the flow and the efficiency of conversion is impaired. If, however, a partition is iiiterposed rnidway betweenthe diverging walls, the angle of divergence between thepartiti'on and each CTI wall is cut in half and each of the new passages thus formed may have the most favorable angle of divergence, and the outer walls of the original passage will then' have'twice the angle of divergence whichl would be permissible without the partition. This principle of securing rapid decelerationwithina restric-tedlength of passage by subdivision, when applied to conical or flaring annular passages, results in theforms of drafttubes described herein. V v

Now referring to the drawings:

v Fig. 1 is avertical. sectional view of a tur bineillustrating the invention.

'tion at therunner R to a substantially Application filed l 'ovember 13, 1,9231 Serial No. 674,461.

Fig. 2 is a'horizontal' sectional view on the line 2 -2 of Fig. 1.

Fig-s. 3 and 1 are vertical sectional views of'modifi'ed forms and 1 Fig. 5 is a vertical sectional view showing theturbine of Fig. 4, for instance, in place in the powerhouse. a a

In the specific embodiment of the invention shown in Figs. 1 and 2*the head cever 7 is supported from the structure 8 at the lower portion of thepit and in turn supports the bearing 9 for the shaft S of the runner R. The flow" entering through the intake 10 passes througl'i the adjustable guide vanes 11 and down on to the runner R with whirling components around the turbine. axis. The runner is of unshrouded propeller type suitable for high specific speed, "and'is positioned in the upper portion of the passage through the casting 12, the upper end 13 0f which is formed toreceive and support the guide vanes 11 and operatingring 14. The

casting 12 is positioned in the fioor'15'of the intake or fiume preferably by being set in the concrete so as to. form aliner forthe draft tube passage. This liner casting 12 flares outwardly from a substantially axial direeradial direction at its lower end 16. 1

A central: conical core 17 is supported from the foundation floor 15 byrods 18-prefera-hly fastened at theirupper endsto the lower end 16,01. the liner 12." The central-conical core 1-7 has an outer surface curvlngfrom substantial'l'y axial at entrance-to substantially radial at discharge-s0 that said core is curved convcxly toward the axis. Between the outer wall 12 andthe inner wall 17 is an intermediate partition 20 separating the draft tube into a plurality of annular passages concentric with the turbine axis andfiaringoutwardly all around. The walls 12, 20 and 17 are so formed and spacedthatx the meridian com-- ponent ofthe velocity-in each annular passage is decelerated as the flow is turned from axial toward radial. (By meridian component or"mer-idian velocity is meant the velocity in mer dian plane, that 1s,"a plane containing tllQflXlS, such. as the plane of the drawing, Fig. I I

Ifthe intermediate partition QOisplac'edso .thatit evenly dilvides the area between, the

walls.- 12 andlT, that is, if the entrance areas at the twoannular passages are equal and if whirling components of velocity.

At the discharge from the draft'tube the the discharge areas are equal then each passage will produce the same amount ofdeceleration of the meridian velocity. That is, if substantially 'half the total flow enters each passage, each half will be decelerated from the same entrance velocity to a common CllS- charge velocity. In order for the entrance areas to be the same, however, the partition will not divide the radial width of the draft tube equally but will fall nearer to the outer wall, so that the product of transverse width of passage and radius to the middle of the passage will be the same in both. At discharge the partition will be midway between the upper wall 16 and the lower wall p In this case of equal subdivision, therefore, it will be noted, first, that theouter passage increases in transverse width in a greater ratio than the inner passage and consequently has a greater average angle of divergence between its outer and inner walls; and, second, the outer passage producesthe given amount of deceleration or enlargement of area in a shorterlength of passage measured in the plane of the figure From both considerations it will be preferable to place the inter-.

mediate partition nearer the outer and upper wall sothat the area across the outer passage is somewhat less than half the total transverse area of the draft tube both atentrance and discharge. This will give more nearly equal efiiciency of conversion of velocity head into pressure head in the two passages, and will give a greater total efficiency. It is, therefore, advantageous so to proportion these passages that the inner passage will receive a larger part of the total flow. The entrance end of the intermediate partition 20 is therefore of such a diameter as to make the annular entrance area of the inner passage greater than that of the outer passage.

p The intermediate partition 20 in dividing the draft tube into a plurality of passages permits a higher rate of deceleration without departure of the flow from the draft tube surface, because each passage canhave the per missible rate of increase inarea independently of the other passage and thetotaljpermissible rate of increase in area is thus approximately doubled, according to the principle previously explained. This makes it possible to accomplish the desired deceleration of the flow within a much shorter lengthof draft tube, redueingthe size and cost of the structure. The walls 12, 20 and 17 being formed as surfaces of revolution offer no obstruction to the whirling components ofthe outflow, and by smoothly spreading and turning this outflow the annular draft tube passages are adapted to recover both the meridian and fiow will retain some measure ofits whirling velocity so that it 1s preferable as shown in Fig. 2 to arrangethe drafttube to be eccentric with relation tothe walls 22 of the outlet passage 23 which outlet passage is thus given somewhat the'form of a volute to collect and turn the whirlingrlines. of flow of the dischargefrom the drafttube. I

In the turbine shown in Fig. 3 the flow ente'rsthrough' the open flame above the fioor 35 and passing through the fixed inclined guide "anes 36 enters the runner R, the guide vanes 36 supporting the central structure 37 carrying the bearing of the'runner shaft S. The outer wall casting or liner 42 flares out wardly and at its lower end carries the bolts 43 from which are supported the central conieal core 4.4 and aplurality of intermediate partitions {l5 and 46, all of said walls being formed as surfaces of revolution flaring outwardly from axial toward a radial direction at discharge. By thus providing a plurality .of intermediate partitions the flow in the draft tubeis still further dividedand guided and the permissiblerate of deceleration between cntrance anddischarge isstill further increased. a

In the turbine shown in Figs. 4 and 5 the outer wall of the draft tube is formed as a liner casting 52 embedded in the'concrete of the floor {i8 and at its lower end this liner casting carries the projecting extension 53 of generally conical form and constructed of plate metal bent into the form of askirt suspended froni said casting 52 The central, conical core 54 is similarly formed of plate metal bent into the form shown and provided with a cap member 55 under. the hub of the runner R. The intermediate partitions 56,

,57.are similarly formedof a'series of plate sections bent into generally conical form and nested one over the other-by lap joints as shown. All of these plate metal members are connected together bythe straps or stays fat their discharge edges. These stays may be inclined as shown to suit the direction of flow. Thefiow from the runner is received in a substantially axial direction and turned outward toward a radial direction and decelerated in the upper portion of the drafttube, and in the lower portion of the draft tube the flow is spread and decelerated all around between concentric conical walls.

This plate metal'construction of the draft l tube is inexpensive and easily formed and gives a higher rate of deceleration of the outflow within a small space (see Fig. 5) being suspended from the floor 18' of the. flume.

This draft tube permits the outlet chamber 58 tobe of-any desired form and, where desired, the central conical core 54 may be continued down to be supported from the floor of this chamber.

While the drafttube of this'inventionis applicable to turbines of all'types, it-is particle larly advantageous for turbines of high res-1,706

specific Speeds, such as the propeller type turbines shown'in the figures. In turbines of low and moderate specific speeds there is a strong tendency at partial gate openings for the discharge to take place through only a part of the runner, namely, that near the outer periphery. The draft tube thus receives a ring of downward flowing water around its outer wall, the inner portion being subject to water not progressing downward but subject to local turbulence and, near theaxis, to upward flow into the runner. In turbines of high specific speed, this tendency is still more pronounced, and takes effect through a large range of gateopenings and even at normal gate in such turbines the flow through the runner may be very unequally distributed. Attempts to improve the turbine performance by subdividing therunner by the addition of intermediate shroud rings or diaphragms in order to separate the flow into distinct annular zones have not shown any material improvement; and in high specific speed turbinessuch diaphragms in the runner are very objectionable from the great increase in, surface friction which they impose due to the high relative velocity between, the runnerand the water. I therefore avoid the use of any shroud rings or diaphragnis in turbines of high specific speed; and in order to improve the conditions in the draft tube 1 and one or more partitions or diaphragms in thedraft tube.

At times when there is a tendency toward a considerable reduction or a reversal o'tflow near the runner hubthere is at the same time a large whirl or rotational component about thefaxis in the water below the runner. By providing a separate annular passage for the waterin the inner portion ofthe draft tube, and by leading this passage outward away from the axis so that the water passing through it materially increases its radial dis tance from the axis in passing from the entrance to the discharge of the passagefl obtain a tube in which the centrifugal "force of the contained water sctsup an outward pressure and maintains a low pressure at the runner discharge. I also provide a sol-id corein the central portion of the tube to avoid the extreme conditions of whirl and inefficient flow, and even the creation of a cavity, which are likely to occur near the axis.

In cases where high eliiciency is important not only at normal gate but also at part gate,

- the innermost annular passage is carried out ward to. substantially the same radius as the outer passage, as in the forms'shownin Figs.

land 3. When small space and reduced first cost are of more relat ve importance than part gate eflieiency, the form oftube shown in Figs.

t and 5 may be used, in which the innermost passage is not carried to as great a radial distance from the axis, but a large total area of discharge for the entire draft tube is pre vidfed Within a small space. In this form of face l'Jou-nded by the discharge edgeof the outer wallet the draft tube, the only part of this area which is not utilized for the discharge ilowbeing the relatively small area of the base of the central core, and thespace taken up by the thickness of the metal in the partitions.

The structure of this invention provides a turbine ofsiniplc and inexpensive form and of small overalldimensions. Thesuspension of the-draft tube from the intake floor avoids thenecessity of any special formation of the eutlet passage and the short length ofthe draft tube is p arti c1 ilarly adapted for shallow outletsi'equiring only a limited depth of excavation. i 1

'lihe subject matter disclosed but. not

clain'iedin this applicationis claimed in my co-peruiling application N0. April 16,1926. I claim:

1. A hydraulic turbine having a runner and 10 ,404, filed draft tube, said draft tube comprising ace-ntral core excluding the flow from the central portion of the draft tube, an outer surface curving progressively from a substantially axial direction at entrance to a direction at discharge inclined at a large angle to the axis,

curving progressively i rom a substantially axialdirection at entranceto a direction at lit) discharge inclined at a large angle tothe axis,

said core and outer surface forming an annular passage continuous wrtlrthe passage through the runner, and intermediate guidingmeanscooperating with said core and outer surface to provide a, plurality of outevardlydirected concentric annular passages surrounding said core and spaced to gradually decelerate the flow. i

3. hydrauli turbineihaving a runner and a draft tube, said draft tube comprising a cen' tral core excluding the flow from the central portion of the draft tube, an .outer'sur'face curving progressively from a siibstantially axial direction at entraneeto a direetion at dischargeinclined at a large angle to the axis, said core andouter surface forn'iingan annular passage continuous with thepassage through the runner, and intermediate guidingmeans cooperating withwsaid core and outer surfacetoprovide a plurality of out-'- wardly directed concentric annular passages surrounding said core and spacedto gradalso ually decelerate the flow, the inner passage having a larger width transverse to the flow at entrance than the outer passage.

'4. A draft tube for a hydraulic turbine comprising a central core excluding the flow from the central portion of the draft tube and means cooperating with said core to provide a. plurality of concentric annular passages surrounding said core, each passage having an outer and an inner surface curving progressively fronra substantially axial direction at entrance toward a radial direction at dischargeand spaced to decelerate the flow while changing its direction between the runner and said discharge.

5. A draft tube for a hydraulic turbine comprising a central core excluding the flow from the central portion of the draft tube, an outer surface flaring outwardly around said core, and a separate guide member interposed between the core and said outer surface so as to provide'a plurality of concentric annular passages progressively curving from a substantially axial direction at entrancetoward a radial direction at discharge and .formed to decelerate the flow while changing its direction between the runner and said discharge.

6. A draft tube for a hydraulic turbine' comprising a plurality of concentric annular passages each passage having outer and inner surfaces curving from a substantially axial direction at'entrance toward a radial direction at discharge and spaced to decelerate the flow while changing its direction, the inner passage having a larger entrance area than the outer passage and more gradual rate of deceleration of the flow.

7. A draft tube for a hydraulic turbine comprising a central core excluding the flow from the central portion of the draft tube and means cooperating with said core to provide a plurality of concentric annular passages surrounding said core, eachpassage' having an outer and an inner surface curving pro-,

gressively from a substantially Y axial direction at entrance toward a radial directionat discharge and spaced to decelerate the flow while changing its directionand discharging the flow from each passage at substantially the same velocity.

8. A draft tube for a hydraulic turbine direction at entrance to a substantially radial direction at discharge and spaced to decelerate the flow while changing its direction between the runner and said discharge.

9. In a hydraulic turbine the combination with a turbine support having a water pas sage therethrough, of means carriedby said support andfornnng the outer wall of a draft tube, an inner core member carried by said support and an intermediate guide interposed between saidiouter wall and said inner core member.

10. In a hydraulic turbine the combination with a turbine support having a water passage therethrough, of means carried by said support and forming the outer wall of a turbinedraft tube flaring outwardly toward a radial direction, an inner core member carried by said support and flaring outwardly toward a radialdirection to novi ean annular flaring passage for the flow from the runner and an intermediate guide interposed more inclined away from the axis and spaced to dccelerate the flow while changingits direction, the innermost surface being provided by a central core member, the contour of the surface of said core member being substantially continuous with that of the runner hub. I

12. A draft tube for a hydraulicturbine. comprising a plurality of concentric annular passages each passage having outer and inner surfaces curving from a substantially axial direction at entrance toward a radial direction at discharge and spaced to decelerate the flow while changing its direction the inner passage having an entrance area at least as great as that of the outer passage. I

13. A draft tube for a hydraulicturbine comprising a plurality of concentric annular passages each passage having outer and inner surfaces curving from a substantially axial direction at entrance towarda radial direction at discharge and spaced to decelerate the flow while changing its direction, the inner and lower passage having a discharge area at least as great as that of the outer and upper passage.

r 14. A drafttuberfor a hydraulic turbine passages each passage'having outer and inner surfaces curving from a substantially axial direction at entrance toward a radial directube for a hydraulic tiu'bine I comprising a plurality of concentric annular I tion at discharge and spaced to decelerate the flow wl11le:,,chan"1n its direction theinner and lower passage having a larger discharge area than the outer and upper passage.

15. In a hydraulic turbine the combination'with a runner of a draft tube comprising a central core member having a contour conj tinuouswith that of the runner'hub, and a plurality of concentric annular passages around said core.

16. In a hy dr aulicturbine the combination creasingiii diametermayhem the runner,

and a pliii'ality concentric ai'ninla-r passages around saidjcoi'e. 1 H

17. A draft tube lor a hydraulic turbine coiiii'prising a relativ'elyshort single passage adj; l p v i plurality or ahiiular passages concentrically dispo ed around said core and flared out Ward from the axis said single pas-f i ing into said annhlai" passages. 18. A liydraulic turbine having arunner and a draft tube, said draft tube comprising a'central core eicludin the fioiv ir'ohithe central portion of the draft tiibe,,an outer surfa ci'irvingprogressively i'ro'in substantially axial direction at entrance to a direction at discharge inclined ata large angle to the are, and intermediate uiding means cooperating Withsaid core and outer surface to provide a plurality of outwardly directed concentric annular passages surroiihding said core and spaced to gradually d lei'fa'te the flow, said guidingineansbeing spaced from said runner so as to leave an undivided passagebetween said riinner and said annular p a e 4 19. A hydraulic turbine having a runner and a. draft tube said draft tube comprising a 'central coreexcludinon the how iroin the centralportion of the than tiibe, an outer surfac'efcurving progressively from a substantially axial direction at entrance to arurection at dischargeihclined at'a-large angle to the axis, said core and outer surface for-in ing an annular passage coiitiiiri'oilsivith the passage through the runner, and interinecliate guiding ineans cooperating with said core and outer surface to, provide a plurality of V outwardly directed concentric anniilar passages snrroiindingsaid co'iie and spaced to gradually decelerate the now, said guiding means being spaced from Said runners'o asto leave an undividedpassage betv'veii said runner and said annular 2a In a hydraulic turbine the combination with a runner of a draft tube having inner; and outer wallsand one or more 1nte rmod1 ate partitions subdividihg the flow and curved from a substantially axial direction at entrance into directions diverging from the axis, said intermediate partitions having relatively small substantially constant thickness compared to'the Width ofthe assages so that substantially all of the area etWeen the inner and outer draft tube Walls is utilized for the entireflow. Y I

21. In a hydraulic turbine the combination with a runner of a draft tube having inner and outer Walls and one or more intermediate partitions subdividing the flow and diverging from the axis in the direction of flow, sa d cent to the runner, a-cenl: a1 core, and a inner Wall being in alignment- With and forming ii continuation ner hub.

22. Anna tube for a hydraulic turbinecomprising central core and a plurality of concentric annular, passages surrounding said core, the Walls of said passages being substantially axial at entrance, and the length oft'li of the surfa ce'of the runinnermost:passage ni'casu'red in ziii'neritlian plane and in the direction offlow being at least equal that the outermost passage; '23, A drafttube for a hydraulic turbine comprising a central core and a plurality of concentric annular passages surrounding saidv core, the Walls Ofl said passages being substantially axial at entranceyand the length of the innermost passage measured 111- a inename plane adm ns direction of now being greater than that of therout'erinost passage.

24. In ahydraulieturbine having a runner, the combination \vitlia sub foundation"struct ure' it'ormingthe top of a discharge pas "ge,

of a draft tube projecting downward into" said passage aiid comprising a plurality of conceit tric tubes spreading outward and dividing the floiv into a pluralityof spreading anniilar streams, the inner tubes beingspa'ced from the tuib'i-ne i'ii'nner to fo'rni a common discharge chamber supported fi oin the outer inost tube WlllGll in turn is supported from said sub-foundation structure.

25; In high specificspeed'liydi'aulic tu'r-' bine ha 1}; a propeller type iinshrouded'rnn- -ner, the combination with a sub' i oundation structure formingthe top-oi a discharge passage, of a" draft tube projecting downward into said passage and comprisinga plurality of'cbii'ceiitii'c vine metal tiibes spreading oiitvvard and ividingthelfiow into a 'pht ralitylif spreading annular streams, th'einr'rer tubes 'bei' g spaced from said runner to form a dischar e chailiberc'omlhon to a plurality of: the passages forine'd'by said tubes and being stipported from the outermost tube foiiiidation structure. 3 k p 26} In a hydraulic turbine having a, run ner the combination with floor structure, of

which in mi-n is suppbrad; from said sub- Ill)" stziyii' aii-s su orted thereby and carrying a 7 bearin Strhct'ure for the runner shaft, a

draft tube receiving the flown-om said run} net and eoihprising plurality of concentric tubes spreading outward and dividing the flow into a plurality of spreading annular streams, the inner tubes being supported from the outermost tube which in turn is supported from said floor structure.

27. In a' hydraulic turbine the combination with a support having a flow passage there through, of arunner in said passage adapted to discharge the flow in a substantially axial direction, inclined stay vanes carried by said v support and in turn carrying a. bearing struccontinuous with the hub of said runner and plurality of tubes surrounding said core and dividing the flow into'a plurality of annular streams spreading outward away from the axis.

an outer surface curving progressively from a substantially axial direction at entrance to a direction at discharge inclined at a large angle to the axis and a centralcore member, said core and outer surface forming an annular passage continuous with the passage through the runner, and intermediate guiding means cooperating with said outer surface to provide a plurality of outwardly directed passages concentric around the axis of. the turbine and spaced to gradually decelerate the flow, said guiding means being spaced from said runner so as to leave an undivided passage between said runner and said annular passages. v I I 29; In a hydraulic'turbine the combination with a runner discharging the fiow axia'lly, ofa draft tube adapted to receive the flow substantially axially and turn. it toward a radial direction while simultaneously gradually and continuously decelerating its ve" uniform thickness forming a draft tube hav ing a plurality-of substantially annularpas sages extending radially outward to permit fluid to be discharged substantially horizontally and said passages being adapted to separate the flow and each passage being adapted to continuously decelerate the flow,

discharged from said runner, and beginning from near the discharge side of said runner.

.28. A hydraulic turbine havingfl'a runner and a draft tube, saiddrait tube comprising 31. In a hydraulic turbine'installation the combination comprising an unshrouded high specific speed propellertype runner having a hub with vanes radially projecting freely therefrom, and means forming a draft tube having a plurality of substantially annular.

passages extending radiallyoutward to permit fluid to be discharged substantially horizontally and said passages being adapted to separate and 'decelerate the how discharged from said runner, andbeginning ina substan' tiallyaxial direction from near the discharge side of said runner and gradually andcontinuously decelerating andturning toward a radial direction as the discharge end of said passages are approached.

32. Ina hydraulic turbine installation the combination comprising anunshrouded high spec fic speed propeller type runner having a'hub'twith vanes radially projecting freely therefrom, and means forming a draft tube having aplurality of substantially annular passages extending radially outward to per mit fluid to be discharged. substantially horizontally and the entrance portion of said means forming said passages be ngjspaced from the discharge sideof said runner where- I by discharged fluid passes through a common unobstructed space prior'to'entering said passages, and said passages being adapted'to separateand decelerate the'flow discharged from said runner. 4

83.1n. a hydraulic turbine the combination with. a runner discharging the flow axially, of a drafttube adapted to receive the fiow'substantially axially and turn it toward a radial direction while simultaneously gradually and continuously decelerating its velocity and comprising anouter spreading wall, anda thin inner partition member of substantially constant thickness curving from axial toward radial and dividing the flow into inner and OuterstreamS each of which is decelerated toconvert velocity head into pressure head, the radius of curvature of said partition in meridiansection being materially greaterthan the radial distance of the entrance portion-of said partition from the turbine axis.

LEWISFERRYMOODY. 

